Intermolecular alkynyl ligand transfer

Intermolecular alkynyl ligand transfer of transition metal complexes is more common than the aryl and alkyl ligand transfer. Alkynyl compounds of Cu(I) and Hg(II) transport the ligand to other transition metals, giving various alkynyl transition metal complexes. [Cu(C=CR)] [171], isolated or generated in situ from the reaction of alkyne, Cul, and base, was employed in preparation of a number of alkynyl complexes of group 5-10 transition metals. The alkynyl hgand transfer is depicted schematically in Eq. 5.46 [172-175]. 

Oxidative addition of aryl (or vinyl) halide to Pd(0) precursor forms the monoarylpalladium complex that is the common intermediate in the catalytic cross-coupling reactions of haloarene with organometallic compounds of main group elements such as Mg, Si, and Sn. Alkynylcopper, formed from alkyne, Cu(I) salt and base in the reaction mixture, transfers the ligand to the above Pd complex, giving an intermediate complex with aryl (or vinyl) and alkynyl ligands bonded to Pd. Reductive elimination of arylacetylene (or enyne) occurs 

The reaction of aryl(alkynyl)palladium complex with Cul in the presence or absence of PPh3 ligand causes formation of alkynylcopper and aryl(iodo)palladium complexes via transmetalation of the alkynyl ligand from Pd to Cu (Eq. 5.49). 

Isomerization of cis- to tra 5-Pt(C=CPh)2(PR3)2 promoted by Cul or HgCl2 was reported to take place via reversible alkynyl transfer between the metal centers 

The alkynyl and iodo ligands of the aryl(iodo)palladium and aryl(alkynyl)-palladium complexes undergo mutual exchange at —30°C (Eq. 5.51) [183]. 

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PMe3)3, reacts with Co(C=CPh)(PMe3)4 to cause intermolecular transfer of the chelating ligand, giving the Co(III) complex with the phenolato and alkynyl... 

Intermolecular addition of terminal alkynes to alkynoates has resulted in some unusual regioselectivity, up to exclusive formation of the G-G bond at the a-carbon." Intramolecular dimerization of a sterically constrained trialkyne proceeding through alkynylpalladium(ii) and yn-enylpalladium(ii) was reported." Interestingly, one of the tolyl groups of the ancillary phosphine ligand was transferred to the remaining alkynyl moiety. 

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